A motor vehicle is mounted with various electronic equipments. An electrical junction box is provided at a suitable location in the motor vehicle to supply electricity and transmit signals to those electronic equipments mounted in the motor vehicle. The term “electrical junction box” used herein collectively means a junction block or box, a fuse block or box and a relay block or box.
This electrical junction box utilizes a waterproof box for preventing water from entering inside the electrical junction box during driving in the rain or during car washing. FIG. 9 shows a cross-sectional perspective view of a conventional waterproof box used in a conventional electrical junction box (refer for example to Japan Patent Application Publication No. 2010-130705).
A conventional waterproof box 201 shown in FIG. 9 includes a body case 203 and a cover 202 mounted to the body case 203 so as to cover an opening of the body case 203. The body case 203 includes a rectangular frame-like peripheral wall 230. The cover 202 includes a rectangular upper wall 223 and a rectangular frame-like peripheral wall 220 extending perpendicularly from an outer periphery of the upper wall 223. This peripheral wall 220 is provided with a water proof groove portion 204 formed at a tip end of the peripheral wall 220 into which a tip end of the peripheral wall 230 of the body case 203 is inserted. This waterproof groove portion 204 is composed of an outer wall 221 positioned outside of the tip end of the peripheral wall 230 and an inner wall 222 positioned inside of the tip end of the peripheral wall 230.
In such manner, with the tip end of the peripheral wall 230 of the body case 203 inserted into the waterproof groove portion 204 of the cover 202, the waterproof box 201 prevents water from entering inside from between the body case 203 and the cover 202 without using a packing.
Furthermore, although it is not shown in FIG. 9, the waterproof box 201 includes an engagement portion formed at one end 202a of the cover 202, and an engagement mating portion formed at one end 203a of the body case 203 with which the engagement portion is engaged. Furthermore, there is provided a lock portion formed at the other end 202b of the cover 202 and a lock receiving portion formed at the other end 203b of the body case 203 and at which the lock portion is locked. When mounting the cover 202 to the body case 203, firstly the engagement portion of the cover 202 is engaged with the engagement mating portion of the body case 203, followed by rotatably moving the cover 202 around the engagement portion as a rotation center and make the lock portion locked at the lock receiving portion, thereby mounting the cover 202 to the body case 203.
In the above-described waterproof box 201, the length of the inner wall 222 adjacent to the one end 202a is formed shorter than the length of the inner wall 222 adjacent to the other end 202b in order to prevent the inner wall 222 of the waterproof groove portion 204 from hitting on the peripheral wall 230 of the body case 203 when rotatably moving the cover 202 around the engagement portion.
The electrical junction box having the waterproof box 201 described above has following drawback. That is, depending on a mounting situation of the electrical junction box on the motor vehicle, water may forcefully splatter onto the cover 202 adjacent to the one end 202a, and in this case, the length of the inner wall 222 adjacent to the one end 202a is not sufficient to prevent water from entering into the waterproof box.